ORGANIC MOLECULES : LIPIDS
Lipids:
- Fats, oils waxes, phospholipids, soaps, steroids
- We eat lipids as part of our food. Our bodies
are capable of producing them as well as
metabolizing them. Next to glucose, fats are the
second most important energy molecules for us.
Unfortunately, as a survival mechanism, we store
them in adipose (fat) cells.
- Function: Long term energy reserve.
- Elements: Carbon, hydrogen, and oxygen but
the H:O ratio is greater than 2:1.
- Structure: neutral fats like hard fats and oils
consist of the monomers fatty acids and glycerol.
- Fatty acids are non-polar chains of carbon and
hydrogen with a carboxylic acid end. A
tremendous number of variations exist between
fatty acids.
- Some are saturated (without double bonds)
- Some are unsaturated (with double bonds)
Various Lipids and Their Structures:
**Neutral Fats- 1 molecule of glycerol in
combination with 1, 2 or 3 molecules of fatty acids.
- Monoglyceride-one fatty acid attached to a
glycerol.
- Diglyceride- two fatty acids attached to a
glycerol.
- Triglyceride- three fatty acids attached to a
glycerol.
a) Fats (saturated fats): Usually of animal origin
and are solid at room temperature.’
Examples : Adipose tissue, Lard, Butter
b) Oils (unsaturated fats): Usually of plant origin
and are usually liquid at room temperature
because of the double bonds.
- Polyunsaturated fats have many double bonds
therefore few hydrogen bonds.
Examples: Vegetable oils
c) Waxes: Relatives of fats, they have fatty acids
joined to a long chain alcohol rather than glycerol.
d) Sterols: Compounds such as the sex hormones,
cholesterol, anabolic steroids and some of the
ingredients of bile.
- Instead of a straight chain of carbons, steroids
are nonpolar ring structures.
- They are insoluble in water therefore considered
a lipid.
- Example: Cholesterol- important part of cell
membrane and the protective cover around nerve
fibers.
- Note: Cholesterol is important, but too much
results in fatty deposits inside arteries. This
narrows the pathway for blood so the heart has to
pump harder to push the blood through the body.
-The result is an increase in blood pressure.
- Cholesterol is the important part of the cell
membrane and the protective cover around nerve
fibers.
- Steroids are able to pass through cell membranes
and combine with receptors in the cell. The
steroid receptor complex activates certain genes
leading to protein synthesis. Increased protein
synthesis increases muscle development.
e) Phospholipids
- Phospholipids are a variation of a triglyceride
where one of the fatty acids is replaced with a
phosphate and a nitrogen-containing group.
- This creates a polar region and consequently
phospholipids can mix with both polar (likes
water) and non-polar (dislikes water) materials.
- Phospholipids are very important in cells as they
form the majority of the cell’s membranes.
- Because they have water-soluble heads and
insoluble tails. They tend to form a thin film on
water with their tails in the air. Like above.
- If surrounded by water they arrange themselves
in a bubble with their tails inward. (This would
be called a rudimentary cell membrane)
- The heads of the phospholipids are polar and are
said to be water loving. (Hydrophilic)
- The Tails of the phospholipds are non polar and
are said to be water hating. (Hydrophobic)
Cell Membrane: